1. Field of the Invention
The present invention relates to the field of soybean production, and more particularly to a method of controlling cyst nematode population in soybeans.
2. Description of the Related Art
Cyst nematodes are responsible for direct loss in soybean yield, and indirect losses due to cost of pesticides and non-optimal use of land or rotation. Soybean cyst nematodes (Heterodera glycines) have a negative economic impact that may exceed $500 million per year in the United States.
Economically significant densities of cyst nematodes usually cause stunting of crop plants. The root system is smaller than for uninfected plants, resulting in leaves showing symptoms of mineral deficiencies with an increased risk of wilting in dry soil conditions. Yield losses are related to the density of cyst nematode present at planting and in severe cases may be substantially above 50% for crops such as soybeans.
Current control methods include the use of chemicals, cultural techniques, and the use of resistant soybean varieties. Nematicides are considered to present significant health risks and cultural control such as crop rotation may be unacceptable to specialist growers or growers with few alternative crops.
Use of resistant soybean varieties does not provide adequate long-term control since cyst nematode race shift occurs. For example, if race 3 is present in a field and the farmer plants a race 3 resistant variety, within one year race shift occurs, i.e., race 3 mutates (race shifts) to race 1, 2, 4, etc. Therefore, the same race 3 resistant soybean variety is again susceptible to the new race spectrum of cyst nematode. Furthermore, cyst nematode is capable of race shifting at a rate faster than the industry can breed or engineer resistant varieties with high yields.
Those concerned with these and other problems recognize the need for an improved process for controlling cyst nematode population in soybeans.